This VCP-DCV practice question tests your understanding of vsphere security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An administrator is configuring a distributed switch and needs to ensure that all virtual machine traffic on a specific VLAN is isolated. The administrator creates a port group with VLAN ID 100. However, a security scanner reports that packets from this VLAN are appearing on other VLANs. Which security policy setting on the distributed switch should the administrator verify?
MAC address changes
Why wrong: This controls whether guest can change MAC.
Forged transmits
Why wrong: Forged transmits control MAC spoofing.
VLAN trunking
VLAN trunking ensures proper tagging.
Promiscuous mode
Why wrong: Promiscuous mode allows all traffic to be seen.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VLAN trunking
The VLAN trunking policy on a distributed switch controls whether a port group can pass multiple VLAN IDs (trunk mode) or is restricted to a single VLAN (access mode). When VLAN trunking is enabled, the port group may forward traffic from VLAN 100 onto other VLANs if the virtual switch is configured to allow it, breaking isolation. The administrator should verify that VLAN trunking is disabled (set to 'Reject') to ensure strict VLAN isolation.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
MAC address changes
Why it's wrong here
This controls whether guest can change MAC.
Forged transmits
Why it's wrong here
Forged transmits control MAC spoofing.
VLAN trunking
Why this is correct
VLAN trunking ensures proper tagging.
Related concept
Read the scenario before looking for a memorised answer.
Promiscuous mode
Why it's wrong here
Promiscuous mode allows all traffic to be seen.
Common exam traps
The trap here is that candidates confuse VLAN trunking (which controls multi-VLAN forwarding) with promiscuous mode (which controls traffic visibility), leading them to incorrectly select promiscuous mode as the cause of VLAN leakage.
Detailed technical explanation
The VLAN trunking policy on a distributed switch implements IEEE 802.1Q trunking, allowing a port group to carry multiple VLANs by preserving VLAN tags in the frame. When set to 'Accept', the switch forwards frames with any VLAN ID, including VLAN 100, to other VLANs if the upstream physical switch is configured for trunking. In contrast, setting it to 'Reject' forces the port group to act as an access port, stripping or blocking non-native VLAN tags, ensuring traffic remains isolated to VLAN 100.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
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FAQ
vSphere Security — This question tests vSphere Security — Read the scenario before looking for a memorised answer..
The correct answer is: VLAN trunking — The VLAN trunking policy on a distributed switch controls whether a port group can pass multiple VLAN IDs (trunk mode) or is restricted to a single VLAN (access mode). When VLAN trunking is enabled, the port group may forward traffic from VLAN 100 onto other VLANs if the virtual switch is configured to allow it, breaking isolation. The administrator should verify that VLAN trunking is disabled (set to 'Reject') to ensure strict VLAN isolation.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This VCP-DCV practice question is part of Courseiva's free VMware certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the VCP-DCV exam.
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